How do I correct someone’s mistake without being rude?
Its like to give nasseha : A sincere advisor must be kind, soft and well-mannered in giving naseehah to others, as this might get the desired response from the one he is advising. One must understand that accepting naseehah is like opening a door, and that the door will not open without the proper key. The one who is given naseeha has a heart that has a lock in some matter - for he has abandoned something that Allah has demanded from him, or has committed something that Allah had forbidden him from. There is no better key to unlock the heart than kindness in giving advice, gentleness in exhortation and softness in speech as the Prophet ( ṣallā llāhu ʿalayhi wasallam ) has said, “Kindness is not to be found in anything but that it adds to its beauty, and it is not withdrawn from anything but it makes it defective.” [Muslim]